Methods for processing battery waste and other lead-contaminated materials

ABSTRACT

The present invention is directed to improved methods for processing battery wastes, battery casing debris and other lead contaminated materials. The improved processes of the present invention provide less environmentally stressful methods for recovering lead from such materials while at the same time producing scrap or recyclable ebonite and plastics having reduced and environmentally acceptable lead and leachable lead levels. Most of the lead is first removed by trammel scrubbing. In another aspect of the present invention ebonite and other hard surface materials to which are adhered lead contaminants are mixed with water and abraded in a high energy scrubber to remove the adhered contaminants prior to separation of the cleaned ebonite from solution. This simple and environmentally preferred hydromechanical process provides clean scrap or recyclable ebonite. In another aspect of the present invention, plastic and other soft materials contaminated with lead are mixed with a solution having a pH greater than about 7, preferably about 1-5 percent-by-weight alkali hydroxide solution, to dissolve lead contaminants. Separation of particulates produces clean scrap or recyclable plastic while carbonation of the wash water permits recovery of lead carbonate. Finally, the present invention provides methods for controlling dust contamination prior to and during processing by spraying the fine, raw materials with an aqueous solution of a wetting agent, preferably about 2 percent-by-weight alkali carbonate, bicarbonate or sesquicarbonate in water.

This is a division of application Ser. No. 07/659,243, filed Feb. 22,1991 now U.S. Pat. No. 5,173,277.

BACKGROUND OF THE INVENTION Field of the Invention

The present invention generally relates to methods for removing leadfrom lead-contaminated wastes and particularly from used lead storagebatteries and battery debris piles. More specifically, the presentinvention is directed to a plurality of environmentally favorablemethods useful to control dust and environmental contamination and torecover the removed lead, together with clean scrap/recyclable ebonite,hard rubbers and plastics. The methods of the present invention employboth hydromechanical separation processes and chemical separationprocesses using more environmentally acceptable chemicals than thoseemployed in the prior art.

Description of the Background

Lead acid storage batteries are comprised of a plurality of lead platesimmersed in a sulfuric acid electrolyte solution contained within anon-conductive case, typically comprised of plastic or hard rubber,e.g., ebonite. Plates of opposite polarity are insulated from oneanother by means of porous separators. Electrochemical power is drawnfrom the plates through conductive lead alloys forming terminals andjoined to the plates. The chemically active materials are sponge lead atthe cathode and lead dioxide at the anode. When these active materialsare electrically connected in the presence of sulfuric acid, anoxidation-reduction reaction creates electrochemical energy and convertsthe lead materials to insoluble lead sulfate. Water, produced as aby-product of the reaction, reduces the concentration of sulfuric acid.As the lead is converted to lead sulfate and the concentration ofelectrolyte reduced, the battery output weakens and the used battery isscrapped.

As a result of the oxidation-reduction reaction from which electricityis produced, used or scrapped batteries, in addition to containing leadand lead dioxide, also contain significant quantifies of lead sulfate ina weak sulfuric acid solution. Scrap batteries have generally beenconsidered valuable only for their lead content. Accordingly, manypatents are directed to methods for recovering the lead from scrapbatteries. For example, see U.S. Pat. Nos. 4,118,219, 3,689,253,3,393,876 and 3,300,043 which disclose various smelting and chemicalmethods for recovering lead from scrap batteries.

Separate and apart from lead recovery are the environmental problemsresulting from used or scrapped batteries, scrap lead and othermaterials contaminated by lead. As environmental knowledge and standardshave increased, the need to process scrap batteries and otherlead-contaminated materials has increased. These environmental problemshave increasingly become important in connection with the clean-up ofmanufacturing, storage and scrap sites contaminated by lead. Theclean-up and removal of lead contamination from such sites and thematerials stored there without producing secondary contamination throughwind-blown, lead-contaminated dust or discharge of water contaminatedwith lead or other chemicals has taken on a new importance.

Of particular concern is the desire to extract the contaminating lead ina recoverable form while producing scrap material having an acceptablelead content and, particularly, an acceptable extractable or leachablelead content which might permit the recovered materials to be recycled.Accordingly, a need has developed for methods for extracting leadcontaminants from the plastic and ebonite portions of used storagebatteries. Methods to produce scrap materials, e.g., ebonite andplastics, meeting more stringent leachable lead concentrations, whethermerely for scrap or for recycle, have intensified.

The methods of the present invention which provide the ability torecover recyclable materials during the clean-up operations and thus tominimize disposal and storage offer significant advantages over theprior art. The present invention provides methods capable of reducingthe leachable lead content of scrap ebonite and plastic below 5 ppm whendetermined by the Extraction Procedure Toxicity test (EPTox). The EPToxtest procedure is set forth at EPA Method 1310. The present inventionoffers methods for meeting even more rigorous standards, e.g., leachablelead determined by the Toxicity Characteristic Leaching Procedure(TCLP), which may be applied in the future. The TCLP test procedure (EPAMethod 1311) is set forth at 40 C.F.R. Part 261, Appendix 11.

Accordingly, the present invention has provided methods for meeting thelong felt but unfulfilled need for environmentally safe methods ofprocessing lead-contaminated materials and reducing the lead andleachable lead content of various materials, e.g., scrap plastics,ebonite, other hard rubbers and other lead-contaminated materials, toprovide clean scrap or recyclable materials.

SUMMARY OF THE INVENTION

The present invention is directed to simple and environmentallypreferred methods for processing lead-contaminated materials to reducethe lead and leachable lead content thereof and to separately removetherefrom lead and scrap/recyclable ebonite and plastic materials. Thepresent invention includes methods for improving dust control, forhydromechanical separation and cleaning and for chemical separationemploying environmentally favored reagents. The methods of the presentinvention are particularly useful in the processing of used storagebatteries and battery debris piles including various plastic, eboniteand other hard rubber materials contaminated with lead and leadcompounds.

In the methods of the present invention the lead-contaminated materialsto be processed are initially crushed or ground. These materialsgenerally include plastics, ebonite and other hard rubbers in additionto lead and various lead compounds. The crushed or ground materials aresized by conventional methods to provide raw, contaminated materialswhich will pass through a 4 inch screen. This material is conveyed to atrammel scrubber where the lead fines are washed from the larger casingfragments with water. On discharge from the trommel, the material issized using screens to between about 10 mesh and about 1.5 inches forfurther processing. Oversize materials are returned to the crusher. Theundersize material consists of lead concentrate from which the lead iseasily removed by conventional methods. The materials which have beensized for further processing comprise ebonite, hard rubbers and plasticswith a reduced lead content. It has been found that materials betweenabout 10 mesh and about 1.5 inches improve the handling and yield,particularly of clean, scrap or recyclable ebonite and plasticmaterials, while reducing fines which must be stabilized for disposal.

After separation of the trammel scrubber wash solution containing thelead fines comprising most of the contaminating lead, the remaining (10mesh to 1.5 inches) solid materials comprise mostly plastics, eboniteand other hard rubbers still contaminated with lead and lead compounds.A mixture of this contaminated material comprising preferably from about30 to about 80 percent-by-weight solids in water is vigorously mixed ina high energy scrubber such as an attrition scrubber. High energyscrubbing abrades the lead contaminants from the surface of the ebonite,hard rubbers and other hard surface, polymeric materials. The cleanedebonite and other hard surface materials are then separated from thewash liquid by conventional screening and floatation separation methods.

Another feature of the present invention are methods to reduce the leadand leachable lead content of scrap/recyclable plastics and other soft,polymeric materials. While attrition scrubbing in water removes theadhered lead contaminants from ebonites and other hard rubbers, mereattrition scrubbing is insufficient to clean softer materials, e.g., thevarious plastics often used in the construction of batteries. Thepresent invention offers methods capable of reducing the lead andleachable lead content of these soft materials. The lead-contaminatedplastics and other soft materials are contacted with an aqueous solutionhaving a pH greater than 7, preferably greater than 10, to dissolve thelead contaminants therefrom. Preferred solutions are aqueous alkali,alkaline earth or ammonium hydroxide solutions in concentrations of fromabout 1.0 to about 10 percent-by-weight of the chosen caustic compound.Most preferred is an aqueous solution comprising about 2percent-by-weight sodium hydroxide. The contaminated plastics and othersoft materials conveniently are mixed with the aqueous caustic solutionin the attrition scrubber. The cleaned plastic is recovered usingconventional screening and floatation separation methods. The dissolvedlead is recovered as lead carbonate by conventional carbonation of thefiltrate.

Wind blown contamination of off-site soils by lead fines andlead-containing dusts is a significant problem. Another feature of theprocesses of the present invention are methods for reducingcontamination from lead fines and lead-containing dusts dispersed fromthe raw materials prior to wet processing. It has been found that suchcontamination is prevented or at least greatly reduced by theapplication of a wetting agent to the piles of excavated materials andto the grizzly, crusher, feeder and trammel scrubber. Favorable resultshave been achieved by spraying a dilute, aqueous solution of aninorganic wetting agent over the crushed or ground raw materials.Preferred wetting agents include alkali, alkaline earth and ammoniumcarbonates, bicarbonates and sesquicarbonates. The most preferredsolution is an aqueous solution comprising about 2 percent-by-weightsodium carbonate or sesquicarbonate. In addition to controlling dust andwind blown lead contamination, application of a dilute solution of suchwetting agents improves the processing of materials in the trammelscrubber and may improve separation of lead fines, thus helping toreduce the lead content of the remaining plastics, ebonite and hardrubbers prior to further processing.

The processes of the present invention provide various methods forreducing the lead and leachable lead content of lead-contaminatedmaterials, particularly the ebonites, hard rubbers and plasticsassociated with used storage batteries. While producing cleanedmaterials of acceptable quality, the methods of the present inventionemploy hydromechanical and chemical separation methods deemedenvironmentally favorable relative to those of the prior art. Further,the methods of the present invention minimize further environmentalcontamination by providing improved dust control and by recycling washsolutions. These and other meritorious features and advantages of thepresent invention will be more fully appreciated from the followingdetailed description and claims.

BRIEF DESCRIPTION OF THE DRAWINGS

Other features and intended advantages of the present invention will bemore readily apparent by the references to the following detaileddescription in connection with the accompanying drawings, wherein:

FIG. 1 is a schematic representation of the initial portion of theprocesses of the present invention illustrating dust control with anaqueous solution of a wetting agent, the sizing of the feed material andthe initial separation of lead fines following mixing in a trammelscrubber;

FIG. 2 is a schematic representation of the middle portion of theprocesses of the present invention illustrating an attrition scrubberused to abrasively and hydromechanically clean adhering leadcontaminants from ebonite, hard rubbers and other low density, hardsurface materials; and

FIG. 3 is a schematic representation of the later portion of theprocesses of the present invention illustrating the cleaning oflead-contaminated plastics by mixing in an attrition scrubber with anaqueous caustic solution, recovery as lead carbonate of the lead removedin the cleaning process and recycle of the wash solution for dustcontrol.

While the invention will be described in connection with the presentlypreferred embodiment, it will be understood that it is not intended tolimit the invention to this embodiment. On the contrary, it is intendedto cover all alternatives, modifications and equivalents as may beincluded in the spirit of the invention as defined in the appendedclaims.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

In the methods of the present invention lead-contaminated materials,particularly waste batteries and battery casing debris are processed toreduce the lead and leachable lead content thereof. The processes of thepresent invention offer methods for controlling lead dust emissions andfor reducing the lead and leachable lead content of plastics, ebonitesand other hard rubbers to acceptable environmental levels whileproviding methods for recovering the removed lead.

The methods of the present invention are employable with anylead-contaminated materials. However, these methods have beenparticularly designed for use with waste storage batteries, batterycasing debris and other materials from lead-contaminated sites. The leadcontaminants are generally present in the form of lead sulfate, leadoxides, lead carbonate and metallic lead.

The waste batteries, casing debris and other lead-contaminated materialsare initially ground or crushed to produce raw materials of a desirablesize for processing. It has been found that raw materials which are toolarge are difficult to process, destructive of the mixing apparatus andproduce unsatisfactory results. On the other hand, materials which aretoo small, i.e., include too many fines, present other processingdifficulties, particularly increased dust and unrecyclable materialswhich must be stabilized for disposal.

The methods of the present invention will first be described withrespect to FIG. 1. The ground or crushed lead-contaminated materials,e.g., waste batteries, battery casing debris and other excavated feedmaterials, are delivered to grizzly screen 10 for sizing. Thosematerials which do not pass through the 4 inch screen of grizzly 10 aretransported via line 12 to crusher 170 for appropriate grinding orcrushing. The materials passing through grizzly 10 move along path 14 tofeeder screen 16. Materials which pass through the 4 inch screen offeeder 16 are transported along line 18 to trammel scrubber 20. Intrammel scrubber 20 the materials are wetted and admixed with water oran aqueous solution. The average residence time in scrubber 20 is about30 minutes and can vary from about ten minutes to an hour or more.Mixing typically is performed at ambient pressure and temperature, i.e.,about 50° F. to about 80° F. No effort is made to control thetemperature. The slurry exits trammel scrubber 20 through screen 22.Material which will not pass through this 1.5 inch screen is returnedvia line 26 to crusher 170 for further sizing. Material which passesthrough screen 22 is conveyed via line 28 to screen 30, a 10 meshseparator. Screens 22 and 30 are washed with water or wetting solutionfrom lines 24 and 32, respectively.

The fine material passing through screen 30 is less than about 10 mesh.This fine material is conveyed via line 34 to conventional screwclassifier 36 where the larger, i.e., greater than about 100 mesh sandsare carried via line 38 for collection of a lead fines concentrate. Mostof the lead originally contaminating the raw materials is removed atthis step. Lead is recoverable, generally by conventional smelting andrefining processes, from this lead fines product. The smaller materials,i.e., less than about 100 mesh fines, are conveyed via line 42 to tank40 for thickening. These very fine materials are thickened by settling,preferably with the additional of a conventional flocculent, e.g., apolymeric flocculent such as Betz polymer 1159. The thickened fines aredelivered from tank 40 to filter 50 via line 46. The filter cake 52 fromfilter 50 is added to the lead fines product. The filtrate from filter50 is returned via line 48 to the input to tank 40. Clarified aqueoussolution from tank 40 is returned via line 44 to screens 22 and 30 forrecycle or to wetting solution tank 172.

It has been found that contamination of the environment by wind blowndust and fines is prevented or at least greatly reduced by theapplication of a dilute aqueous solution of a wetting agent. Theexcavated material maintained in storage piles about the site should beso wetted. Wetting is achieved by spraying or misting the raw materialswith a dilute aqueous solution of a wetting agent until visibly coatedand wetted. Further, it has been found beneficial to spray or mist thewetting solution onto the materials in the grizzly, crusher, feeder andtrammel scrubber to minimize dust and achieve maximum benefit. Contactof the raw materials with the dilute aqueous solution of a wetting agentprior to separation in trammel scrubber 20 may also improve removal oflead contaminants into the lead fines product portion exiting thescrubber.

The wetting solution is prepared and stored in tank 172. The solution isprepared using make-up or recycle water delivered through line 44 formixing with a wetting agent. Additionally, the wash water from the finalplastic cleaning process produced at 168 (FIG. 3) may also be used formake-up. The wetting solution is applied by conventional sprayers ormisters 174 to the excavated feed material, grizzly 10, crusher 170,feeder 16 and trammel 20. While conventional organic surfactants, e.g.,detergents, may be used as wetting agents, they are not preferred due tofoaming characteristics and a desire to minimize the environmentalimpact of the wash solutions. Because of their compatibility with theremaining steps of the process and because of the ability to recycleprocess solutions, inorganic wetting agents are preferred. Recycle ofthese solutions significantly reduces the volume of waste water whichmust be discharged off site and thereby improves the environmentalsuitability of the processes of the present invention. Preferred wettingagents include the alkali, alkaline earth and ammonium carbonates,bicarbonates and sesquicarbonates. Aqueous solutions comprising about0.5 percent-by-weight or more wetting agent in water have been foundeffective. Because little improvement is observed at concentrationsgreater than about 3 percent-by-weight, preferred concentrations areabout 1 to about 3 percent-by-weight. On the basis of fieldobservations, the most preferred solution is presently believed to be anaqueous solution comprising about 2 percent-by-weight sodiumsesquicarbonate.

The improvement in dust control achieved by using dilute solutions of aninorganic wetting agent was demonstrated by a simple experiment.Powdered ebonite was prepared by grinding and sizing an ebonite sampleto less than about 65 mesh. The sized sample was dried and stored in asealed container. Sodium carbonate solutions of varying concentrations(0.5, 1.0, 2.0, 3.0 and 6.0 percent-by-weight) were prepared bycombining the appropriate weight of sodium carbonate with deionizedwater. Tests were conducted with a solid:liquid ratio to provide a 20percent solids slurry. Tests were conducted in 400 ml glass beakers witha magnetic stirrer set at a constant speed to provide vigorous stirring.Each sample was tested by first placing 125 grams of the sodiumcarbonate test solution in the beaker, adding the stirring bar andactivating the stiffer to the predetermined speed. Twenty-five grams ofdried and sized, powered ebonite was carefully placed on the surface ofthe stirring solution. The time from placing the powdered ebonite on thesolution until the ebonite was completely drawn into solution, i.e.,completely wetted, was measured. Deionized water was run as a control.The results are illustrated in Table I.

                  TABLE 1                                                         ______________________________________                                        Sodium Carbonate Concentration                                                                     Settling Time                                            (percent-by-weight)  (minutes)                                                ______________________________________                                        0                    19.0                                                     0.5                  7.5                                                      1.0                  5.0                                                      2.0                  3.0                                                      3.0                  2.5                                                      6.0                  2.5                                                      ______________________________________                                    

This test illustrates the remarkable improvement in wetting achieved byusing a dilute aqueous solution of an inorganic wetting agent. This testfurther illustrates that no significant improvement is achieved atconcentrations greater than about 2 percent-by-weight.

Referring now to FIG. 2, the output from screen 30 comprising materialfrom which most, but not all the lead contamination has been removed andwhich has been sized to between about 10 mesh and about 1.5 inch isdelivered via line 54 to heavy media separator 60 for separation ofmetallic lead and other heavy materials using magnetite delivered vialine 58. Make up water is delivered via lines 56 to separator 60 andscreen 62. The materials leaving heavy media separator 60 are passedthrough screen 62 with the oversized materials being removed by screen62 and carried away via line 64. The fines from the wash are deliveredvia line 66 to the lead fines product or to stabilization, depending onthe lead content. The remaining float materials comprise essentially theplastics, e.g., polypropylene, polyethylene, PVC and other relativelysoft polymerization products, together with low density, hard surface,hard polymerization products, e.g., ebonite and other hard rubbers.These materials are delivered via line 68 to attrition scrubber 70.

Because attrition scrubbing abrades not only the lead contaminantsadhered to the surface of the hard polymeric materials, but also aportion of the surface of those materials, size of the startingmaterials, along with the scrubbing conditions, including scrubbingspeed and residence time in the scrubber, are important factors. Propersizing of the materials, particularly the hard polymeric materials, hasbeen found to be particularly important in recovery of improved yieldsof recyclable ebonite and other hard rubbers. Minimization of theebonite fines which must be stabilized for disposal and maximization ofcleaned, recyclable ebonite is important to the economics of thesecleaning processes. In the past, attrition scrubbers used for processingother materials generally employed smaller materials, i.e., materialssized to be less than about 0.375 inch. It has been found in the presentmethods that those small starting materials produce an unacceptably lowratio of recyclable scrap to fines which must be stabilized fordisposal. Use of larger materials, preferably those as large as about 1inch to about 1.5 inch increases the ratio of recyclable ebonite tofines. With materials sized to less than about 0.375 inch, the ratio ofrecyclable ebonite to fines was about 1:1; with materials sized to lessthan about 1 inch, the ratio of recyclable ebonite to fines increased toabout 4:1; and with materials sized to less than about 1.5 inch, theratio of recyclable ebonite to fines was at least about 5:1.

Attrition scrubber 70 provides a high energy scrubber for vigorousscrubbing of the materials delivered via line 68 from heavy mediaseparator 60. Exemplary attrition scrubbers are manufactured by DenverEquipment Co. in various sizes and with various mixing powers. Attritionscrubber 70 includes a plurality of agitators 72 turned by a pluralityof motors 74. In order to achieve vigorous scrubbing it is been founddesirable to operate attrition scrubber 70 at between about 800 to about1500 rpm. Make up water is added to attrition scrubber 70 via line 76.While satisfactory results have been obtained with solid concentrationsas high as about 80 percent-by-weight in water and as low as about 30percent-by-weight, it has been found desirable to operate attritionscrubber 70 with solutions comprising from about 60 to about 80percent-by-weight solids in water. It is desirable to maintain a highconcentration of solids to increase the efficiency of the abrasivescrubbing. However, concentrations which are too high will slow ordamage the scrubber. On the other hand, concentrations which are too lowdo not provide the required abrasive contact. Sufficient lead removal isobtained with residence times in attrition scrubber 70 as low as 15minutes. While residence times may be up to two hours or more, it hasbeen found desirable to maintain residence times between about 15minutes and 1 hour, preferably about 30 minutes. While the scrubbingtemperature may range between the freezing and boiling points of thescrubbing solution, i.e. water, scrubbing typically is performed atambient temperature and pressure. Because heat is generated by thevigorous scrubbing and abrasive action and no effort is made to controlthe temperature, temperatures above ambient are common in scrubber 70.

The output from attrition scrubber 70 is delivered via line 78 to screen80. Using make-up water delivered from line 82, the cleaned ebonite andplastic materials greater than about 10 mesh are passed via line 96 toconventional water separator 100 where the plastics float higher thanthe ebonites and are readily separated and removed by conventionalmeans. The clean ebonite is removed from water separator 100 via line104 while the plastic is removed via line 102 for further processing.Line 84 delivers the wash water from screen 80, including the leadcontaminants abraded from the ebonite and the hard rubbers to tank 84for thickening. Thickening is achieved by settling, preferably withaddition of a standard flocculent, e.g., a polymeric flocculent such asBetz polymer 1154. The thickened sludge, including abraded leadcontaminants, is conveyed via line 88 to filter 90 from which the filtercake 92, containing the abraded lead contaminants and ebonite fines isremoved for stabilization. The filtrate from filter 90 is recycled vialine 94 to thickening tank 84. Clarified solution from tank 84 isdelivered via line 86 for recycle via inlets 56, 76 or 82 to,respectively, the heavy media separator 60, attrition scrubber 70 orscreen 80.

The plastic recovered at 102 after attrition scrubbing with waterremains contaminated with lead. It is believed that attrition scrubber70 is able to effectively clean hard surface materials, e.g., eboniteand hard rubbers, because the contaminating lead which is adhered to andin the porous surface thereof is readily abraded by the vigorousadmixing in the attrition scrubber. On the other hand, attritionscrubber 70 is unable to remove sufficient lead contaminants from softmaterials, e.g., plastics, which are apparently not readily abraded bythe vigorous scrubbing action. Accordingly, it has been found necessaryto further process plastic and other soft materials. An additionalprocessing unit may be employed or the material may simply be stockpiledand reprocessed through attrition scrubber 70. This additionalprocessing involves contacting the soft, plastic materials with a basicaqueous solution to dissolve the contaminating lead.

FIG. 3 illustrates in detail the method for further processing theselead-contaminated plastic materials. Lead-contaminated plastic instockpile I 10 is delivered via conveyor 1 12 to attrition scrubber 120for vigorous, high energy scrubbing. Attrition scrubber 120 is equippedwith a plurality of agitators 122 driven by a plurality of motors 124.Scrubbing conditions, i.e., mixing speed, temperature, pressure,residence time and the like are the same as discussed above with respectto scrubber 70. Because of the lower density of plastic, it may not bepossible to achieve the solids ratio preferred with the ebonites andhard rubbers. Attrition scrubber 120 should be operated with a solidsratio of about 30 to about 80 percent-by-weight solids, and preferablyabout 30 to about 60 percent-by-weight solids to achieve maximumefficiency of lead dissolution.

The caustic leach solution is prepared in mixing tank 130 and deliveredvia pump 126 though line 128 to attrition scrubber 120. The leachsolution should be at a pH greater than about 7 and preferably greaterthan about 10. The preferred leaching solution is an aqueous hydroxidesolution, preferably an alkali, alkaline earth or ammonium hydroxide,and most preferably sodium hydroxide. The caustic compound, preferablysodium hydroxide, is present between about 0.5 and about 10 or morepercent-by-weight in water, more preferably between about 1 and about 5percent-by-weight, most preferably about 2 percent-by-weight in aqueoussolution. The mixture of plastic and solution from attrition scrubber120 is delivered via line 132 to wash screen 134. The plastic is removedto conventional screw classifier 140 where any residual insolublematerials with densities greater than water are removed via line 138.From classifier 140, the cleaned, plastic material is delivered via line142 to second screen 150 where wash water from source 144 is added. Thecleaned, plastic material floating on screen 150 is removed via line 146to a clean product receptacle.

The wash water from screen 150 is drained through line 148 and pumpedvia pump 152 through line 148 for combination with the wash water fromscreen 134 pumped via line 154 using pump 156. This filtrate comprisesthe aqueous hydroxide solution containing dissolved lead. This solutionis delivered to carbonator 160 where carbon dioxide from tank 158 isadded via line 162 to convert the lead to lead carbonate forprecipitation and removal. The output of carbonator 160 is delivered vialine 164 to tank 170 for thickening by precipitation. The settled leadcarbonate may be recovered via line 166 while the clarified solution isdrawn from tank 170 via line 168 for use in site dust control (FIG. 1).

Effectiveness of the processes of the present invention may be seen bythe following example wherein several different starting materials weretreated by the processes of the present invention. The resulting eboniteand plastic materials were analyzed for leachable lead in accord withthe EPTox procedure and the results reported in Tables II and III,respectively.

                                      TABLE II                                    __________________________________________________________________________    ATTRITION SCRUBBING OF EBONITE WITH WATER*                                             Sample A   Sample B   Sample C                                                Lead                                                                              EPTox Lead                                                                           Lead                                                                              EPTox Lead                                                                           Lead                                                                              EPTox Lead                                          (ppm)                                                                             (ppm)  (ppm)                                                                             (ppm)  (ppm)                                                                             (ppm)                                      __________________________________________________________________________    Bench Test:                                                                            450 3.5    180 1.2    310 0.2                                        Pilot Test:                                                                            300 3.6    --  --     --  --                                         Bulk Processing:                                                                       400 3.6    320 3.8    490 2.4                                        Field    510 2.4    --  --     --  --                                         Demonstration:                                                                __________________________________________________________________________     *Ebonite was scrubbed in water at 60-70 percentby-weight solids (ebonite)     for 30 minutes.                                                          

                  TABLE III                                                       ______________________________________                                        ATTRITION SCRUBBING OF PLASTIC WITH CAUSTIC*                                  Scrubbing                                                                              Sample D            Sample E                                         Time     Lead    EPTox Lead  Lead  EPTox Lead                                 (min.)   (ppm)   (ppm)       (ppm) (ppm)                                      ______________________________________                                         0       3290    23.3-36.7   2610  19.5                                       10       490     10.0        700   2.1                                        20       950     3.2         480   0.6                                        30       500     0.9         710   0.7                                        ______________________________________                                         *Plastic was scrubbed in 2 percentby-weight sodium hydroxide at 35            percentby-weight solids (plastic).                                       

The foregoing description of the invention has been directed in primarypart to a particular preferred embodiment in accordance with therequirements of the patent statutes and for purpose of explanation andillustration. It will be apparent, however, to those skilled in the artthat many modifications and changes in the specifically described systemmay be made without departing from the true scope and spirit of theinvention. Therefore, the invention is not restricted to the preferredembodiments described, but covers all modifications which may fallwithin the scope of the following claims.

What is claimed is:
 1. A method for reducing the lead and leachable leadcontent of fragments of lead storage batteries and battery debriscomprising hard surface materials to which are adhered leadcontaminants, comprising:contacting said fragments with an aqueoussolution of a soluble inorganic salt to convert lead-contaminants insaid fragments to a stable, lead slat insoluble in said solution;abrading said insoluble lead salt from said fragments by scrubbing in ahigh energy scrubber rotating at about 800 to about 1500 rpm a mixturecomprising from about 30 to about 80 percent-by-weight of said fragmentsin water; and separating clean fragments from which said insoluble leadsalt has been abraded.
 2. The method of claim 1 wherein said insolublelead salt is lead carbonate.
 3. The method of claim 1 wherein saidsoluble inorganic salt is selected from the group consisting of thesoluble carbonates, bicarbonates, sesquicarbonates and mixtures thereof.4. The method of claim 1 further comprising washing said clean fragmentswith an aqueous wash selected from the group consisting of water andsaid aqueous solution.
 5. A method for reducing the lead and leachablelead content of fragments of lead storage batteries and battery debriscomprising plastics to which are adhered lead contaminants such as leadsulfate, lead oxides, metallic lead and mixtures thereof,comprising:leaching said lead contaminants from aid fragments sizedbetween about 10 mesh and about 1.5 inches by scrubbing in a high energyscrubber rotating at about 800 to about 1500 rpm a mixture of saidfragments with an aqueous solution comprising from about 1 to about 3percent-by-weight sodium hydroxide for a time of about 15 minutes toabout 2 hours and at a temperature between about 40° F. and about 120°F., said mixture comprising from about 30 to about 60 percent-by-weightsolids; transferring said mixture to a floatation tank; and separatingclean plastics from said aqueous solution containing dissolved leadcontaminants by removing floating plastics from the surface of saidsolution in said floatation tank.
 6. A method for reducing the lead andleachable lead content of fragments of lead storage batteries andbattery debris comprising plastics to which are adhered leadcontaminants, comprising:leaching said lead contaminants from saidfragments with an aqueous solution having a pH greater than about 7; andseparating clean plastics from said aqueous solution containing theleached contaminants by floatation after scrubbing in a high energyscrubber rotating at about 800 to about 1500 rpm a mixture of saidfragments in said aqueous solution.
 7. The method of claim 6 wherein thepH of said aqueous solution is greater than about
 10. 8. The method ofclaim 6 wherein said solution comprises an aqueous solution of anhydroxide.
 9. The method of claim 8 wherein said hydroxide is selectedfrom the group consisting of the alkali hydroxides, the alkaline earthhydroxides, ammonium hydroxide and mixtures thereof.
 10. The method ofclaim 9 wherein said hydroxide is sodium hydroxide.
 11. The method ofclaim 8 wherein said aqueous solution comprises from about 0.5 to about10 percent-by-weight of said hydroxide.
 12. The method of claim 6wherein said aqueous solution comprises from about 1 to about 3percent-by-weight sodium hydroxide.
 13. The method of claim 6 whereinsaid mixing is performed in an attrition scrubber and said mixturecomprises from about 30 to about 80 percent-by-weight solids.
 14. Themethod of claim 6 wherein said fragments are leached for about 15minutes to about 2 hours.
 15. The method of claim 6 further comprisingconverting lead which is leached into said aqueous solution to leadcarbonate and removing the lead carbonate by precipitation andseparation from said aqueous solution.
 16. The method of claim 6comprising sizing said fragments to between about 10 mesh and about 1.5inches prior to said leaching.